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The Environment / "Another Hockey Stick Illusion"?
« on: 13/04/2011 10:25:00 »
I came across this blog while searching for detailed pictures of ice extracted from deep down an ice sheet. I have a question that has been puzzling me for over a year now and remains unanswered despite asking it of experts in the subject. My question in a nut shell to the scientists here is “why do paleo-climatologists use collision diameter in preference to kinetic diameter when considering the migration of air molecules through firn and ice”? Here is some background.
The photo shown on your “Climate Change and Ice Cores” thread (http://www.thenakedscientists.com/HTML/content/interviews/interview/643/) is a beauty as a starter because it clearly shows the air pockets which are claimed to hold air having the same composition as when it was captured from the atmosphere thousands of years ago. This sounds like a wonderful natural archive which simply has to be emptied of air which can then be analysed to provide what Professor Richard Alley refers to as “the gold standard” for exposing the ancient atmospheric make-up to – but is it?
Dr Eric Wolff from the British Antarctic Survey thinks so. When discussing the natural global warming that has occurred since the Little Ice Age (it always warms between ice ages, then cools again towards another one) he says “ .. the arguments about whether global warming is real hinge on four aspects. The first one is the physics that tells us to expect that when we get more carbon dioxide in the atmosphere it should get warmer. The second one is whether carbon dioxide has actually increased in the atmosphere, and that's what I'm best at because that's what we can see from ice cores. The third one is whether in the past that's caused climate change. And we can see in the ice cores that at least every time carbon dioxide's changed in the past, then it has warmed. So there's no counter evidence .. ”.
Let’s look at each in turn:
- physics tells us that if everything else that controls the mean global temperature remains unchanged then increasing CO2 will cause an insignificant amount of warming amounting to about 1C for a doubling in concentration from 300 to 600ppm. The present atmospheric CO2 content is estimated (from readings on top of an extinct volcano in the “ .. exhaust plume of massive oceanic outgassing in the Eastern Equatorial Pacific .. ” - http://judithcurry.com/2011/02/26/agreeing/#) to be about 400ppm, having risen from an estimated 300ppm in 1850,
- the ice cores are only able to show us that the concentration of residual CO2 in the air bubbles reduces the lower the bubble is in the ice sheet until a depth is reached when the residual level changes relatively little around a mean value of about 280ppm (Fig 2 in http://www-das.uwyo.edu/~geerts/cwx/notes/chap01/icecore.html)
- an important piece of information about this has been withheld. “ .. On the basis of atmospheric CO2 data obtained from the Antarctic Taylor Dome ice core and temperature data obtained from the Vostok ice core, Indermuhle et al. (2000) studied the relationship between these two parameters over the period 60,000-20,000 years BP (Before Present). One statistical test performed on the data suggested that shifts in the air's CO2 content lagged shifts in air temperature by approximately 900 years, while a second statistical test yielded a mean lag-time of 1200 years. Similarly, in a study of air temperature and CO2 data obtained from Dome Concordia, Antarctica for the period 22,000-9,000 BP -- which time interval includes the most recent glacial-to-interglacial transition -- Monnin et al. (2001) found that the start of the CO2 increase lagged the start of the temperature increase by 800 years. Then, in another study of the 420,000-year Vostok ice-core record, Mudelsee (2001) concluded that variations in atmospheric CO2 concentration lagged variations in air temperature by 1,300 to 5,000 years. .. ” (http://www.co2science.org/articles/V6/N26/EDIT.php).
I have been researching the second of Dr. Wolff’s points for over a year now, exchanging opinions with experts in relevant fields such as Professor Alley, Professor Jeff Severinghaus, Professor Michael Bender, Professor Hartmut Frank, Professor Zbiniew Jaworowski, Dr. William Connolley (you may know him), etc. I think that is quite a balanced selection of experts and my conclusion, after reading lots and lots of relevant papers, is this. Due to its much smaller kinetic diameter, CO2 is preferentially fractionated out of the air pockets when the escape routes have reduced to a size in the lowest levels of the firn that prevents the escape of the larger N2, O2 and CH4 molecules. This results in the residual air “trapped” in pockets after close-off are depleted in CO2 while the air above is enriched. I say “trapped” because even after close-off it is still possible for further depletion in CO2 to take place due to H-bond breaking through the ice crystal lattice.
If you are interested in more of this you’ll find some on the Climate Conversation blog (http://www.climateconversation.wordshine.co.nz/2011/03/fallen-snow/#comment-46211 and http://www.climateconversation.wordshine.co.nz/2011/03/its-not-warming-you-nitwit-its-cooling/#comment-45360.
As I said before, trying to simplify science that is poorly understood is fraught with danger and the processes and drivers of the different global climates. Professor Barry Brook, previously Professor but now Director of Climate Change at Adelaide University said a couple of years ago “ .. There are a lot of uncertainties in science, and it is indeed likely that the current consensus on some points of climate science is wrong, or at least sufficiently uncertain that we don’t know anything much useful about processes or drivers. But EVERYTHING? Or even most things? Take 100 lines of evidence, discard 5 of them, and you’re still left with 95 and large risk management problem .. ” (http://bravenewclimate.com/2009/04/23/ian-plimer-heaven-and-earth/). The significant part of that comment is “we don’t know anything much useful about processes or drivers” (Please read the full comment as Professor Brook gets rather upset when readers are unable to ascertain the full context of what he said.)
It strikes me as being perhaps disingenuous to try to imply that only 5% of the science is uncertain by plucking those 100, 95 and 5 lines of evidence out of the air, but it’s a bit like what the IPCC does when trying to quantify “expert opinion”. Maybe Brook has the same attitude as Professor Stephen Schneider "To capture the public imagination, we have to offer up some scary scenarios, make simplified dramatic statements and little mention of any doubts one might have. Each of us has to decide the right balance between being effective, and being honest" (http://www.john-daly.com/schneidr.htm).
I’d be very interested to know what your opinion is of scientists being what is, in my opinion, simply dishonest. It is scientists like Schneider who make lay people like myself trust scientists even less than we trust politicians and used-car salespersons. Talking about politicians (and other power-hungry individuals), isn’t that where all of this CACC propaganda is coming from?
Best regards, Pete Ridley
The photo shown on your “Climate Change and Ice Cores” thread (http://www.thenakedscientists.com/HTML/content/interviews/interview/643/) is a beauty as a starter because it clearly shows the air pockets which are claimed to hold air having the same composition as when it was captured from the atmosphere thousands of years ago. This sounds like a wonderful natural archive which simply has to be emptied of air which can then be analysed to provide what Professor Richard Alley refers to as “the gold standard” for exposing the ancient atmospheric make-up to – but is it?
Dr Eric Wolff from the British Antarctic Survey thinks so. When discussing the natural global warming that has occurred since the Little Ice Age (it always warms between ice ages, then cools again towards another one) he says “ .. the arguments about whether global warming is real hinge on four aspects. The first one is the physics that tells us to expect that when we get more carbon dioxide in the atmosphere it should get warmer. The second one is whether carbon dioxide has actually increased in the atmosphere, and that's what I'm best at because that's what we can see from ice cores. The third one is whether in the past that's caused climate change. And we can see in the ice cores that at least every time carbon dioxide's changed in the past, then it has warmed. So there's no counter evidence .. ”.
Let’s look at each in turn:
- physics tells us that if everything else that controls the mean global temperature remains unchanged then increasing CO2 will cause an insignificant amount of warming amounting to about 1C for a doubling in concentration from 300 to 600ppm. The present atmospheric CO2 content is estimated (from readings on top of an extinct volcano in the “ .. exhaust plume of massive oceanic outgassing in the Eastern Equatorial Pacific .. ” - http://judithcurry.com/2011/02/26/agreeing/#) to be about 400ppm, having risen from an estimated 300ppm in 1850,
- the ice cores are only able to show us that the concentration of residual CO2 in the air bubbles reduces the lower the bubble is in the ice sheet until a depth is reached when the residual level changes relatively little around a mean value of about 280ppm (Fig 2 in http://www-das.uwyo.edu/~geerts/cwx/notes/chap01/icecore.html)
- an important piece of information about this has been withheld. “ .. On the basis of atmospheric CO2 data obtained from the Antarctic Taylor Dome ice core and temperature data obtained from the Vostok ice core, Indermuhle et al. (2000) studied the relationship between these two parameters over the period 60,000-20,000 years BP (Before Present). One statistical test performed on the data suggested that shifts in the air's CO2 content lagged shifts in air temperature by approximately 900 years, while a second statistical test yielded a mean lag-time of 1200 years. Similarly, in a study of air temperature and CO2 data obtained from Dome Concordia, Antarctica for the period 22,000-9,000 BP -- which time interval includes the most recent glacial-to-interglacial transition -- Monnin et al. (2001) found that the start of the CO2 increase lagged the start of the temperature increase by 800 years. Then, in another study of the 420,000-year Vostok ice-core record, Mudelsee (2001) concluded that variations in atmospheric CO2 concentration lagged variations in air temperature by 1,300 to 5,000 years. .. ” (http://www.co2science.org/articles/V6/N26/EDIT.php).
I have been researching the second of Dr. Wolff’s points for over a year now, exchanging opinions with experts in relevant fields such as Professor Alley, Professor Jeff Severinghaus, Professor Michael Bender, Professor Hartmut Frank, Professor Zbiniew Jaworowski, Dr. William Connolley (you may know him), etc. I think that is quite a balanced selection of experts and my conclusion, after reading lots and lots of relevant papers, is this. Due to its much smaller kinetic diameter, CO2 is preferentially fractionated out of the air pockets when the escape routes have reduced to a size in the lowest levels of the firn that prevents the escape of the larger N2, O2 and CH4 molecules. This results in the residual air “trapped” in pockets after close-off are depleted in CO2 while the air above is enriched. I say “trapped” because even after close-off it is still possible for further depletion in CO2 to take place due to H-bond breaking through the ice crystal lattice.
If you are interested in more of this you’ll find some on the Climate Conversation blog (http://www.climateconversation.wordshine.co.nz/2011/03/fallen-snow/#comment-46211 and http://www.climateconversation.wordshine.co.nz/2011/03/its-not-warming-you-nitwit-its-cooling/#comment-45360.
As I said before, trying to simplify science that is poorly understood is fraught with danger and the processes and drivers of the different global climates. Professor Barry Brook, previously Professor but now Director of Climate Change at Adelaide University said a couple of years ago “ .. There are a lot of uncertainties in science, and it is indeed likely that the current consensus on some points of climate science is wrong, or at least sufficiently uncertain that we don’t know anything much useful about processes or drivers. But EVERYTHING? Or even most things? Take 100 lines of evidence, discard 5 of them, and you’re still left with 95 and large risk management problem .. ” (http://bravenewclimate.com/2009/04/23/ian-plimer-heaven-and-earth/). The significant part of that comment is “we don’t know anything much useful about processes or drivers” (Please read the full comment as Professor Brook gets rather upset when readers are unable to ascertain the full context of what he said.)
It strikes me as being perhaps disingenuous to try to imply that only 5% of the science is uncertain by plucking those 100, 95 and 5 lines of evidence out of the air, but it’s a bit like what the IPCC does when trying to quantify “expert opinion”. Maybe Brook has the same attitude as Professor Stephen Schneider "To capture the public imagination, we have to offer up some scary scenarios, make simplified dramatic statements and little mention of any doubts one might have. Each of us has to decide the right balance between being effective, and being honest" (http://www.john-daly.com/schneidr.htm).
I’d be very interested to know what your opinion is of scientists being what is, in my opinion, simply dishonest. It is scientists like Schneider who make lay people like myself trust scientists even less than we trust politicians and used-car salespersons. Talking about politicians (and other power-hungry individuals), isn’t that where all of this CACC propaganda is coming from?
Best regards, Pete Ridley